Bifurcated intraluminal prostheses construction and methods

ABSTRACT

The present invention provides modular bifurcated intraluminal tubular prostheses, particularly stents and stent-grafts, for the treatment of disease conditions, particularly aneurysms. Modular sections of the prostheses, or “prosthetic modules,” may be selectively assembled to form a prosthesis having characteristics which are tailored to the specific requirements of the patient, including branch angle and branch lumen sizes which match the patients vascular geometry. A Y-connector prosthetic module structure provides support and separation for each of the adjacent branching lumens. Radiopaque markers on the prostheses promote alignment between prosthetic modules and with the body lumen system.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to endoluminal tubularprostheses, such as stents, stent-grafts, and other structures. Moreparticularly, the present invention provides bifurcated prosthesisstructures having properties which are tailored for individual bodylumens, including blood vessels, particularly for the treatment ofabdominal and other aneurysms.

[0003] Vascular aneurysms are the result of abnormal dilation of a bloodvessel, usually resulting from disease and/or genetic predisposition,which can weaken the arterial wall and allow it to expand. Whileaneurysms can occur in any blood vessel, most occur in the aorta andperipheral arteries, with the majority of aortic aneurysms occurring inthe abdominal aorta, usually beginning below the renal arteries andoften extending distally into one or both of the iliac arteries.

[0004] Aortic aneurysms are most commonly treated in open surgicalprocedures where the diseased vessel segment is bypassed and repairedwith an artificial vascular graft. While considered to be an effectivesurgical technique, particularly considering the alternative of ausually fatal ruptured abdominal aortic aneurysm, conventional vasculargraft surgery suffers from a number of disadvantages. The surgicalprocedure is complex and requires experienced surgeons and well equippedsurgical facilities. Even with the best surgeons and equipment, however,patients being treated frequently are elderly and weakened fromcardiovascular and other diseases, reducing the number of eligiblepatients. Even for eligible patients prior to rupture, conventionalaneurysm repair has a relatively high mortality rate, usually from 2% to10%. Morbidity related to the conventional surgery includes myocardialinfarction, renal failure, impotence, paralysis, and other conditions.Additionally, even with successful surgery, recovery takes severalweeks, and often requires a lengthy hospital stay.

[0005] In order to overcome some or all of these drawbacks, endovascularprosthesis placement for the treatment of aneurysms has been proposed.Although very promising, many of the proposed methods and apparatussuffer from undesirable limitations. In particular, proper sizing ofendovascular prostheses can be problematic.

[0006] Proper matching of the prosthesis to the branching blood vesselis critical to the treatment of an aneurysm. The prosthesis preferablyextends axially beyond the weakened portion of the blood vessel toanchor securely in the healthy vessel wall. However, the cross-sectionalsize and axial length of individual blood vessels vary considerablybetween patients. Even within a patient, the cross-section andresilience of a lumen wall can vary considerably along its axial length,and the location and extent of the aneurysm will differ with differentpatients. Additionally, each prosthesis must be carefully constructedand handled, making it extremely costly to provide and maintain thelarge selection of prostheses required for proper fitting of everyindividual patient.

[0007] Known branching intraluminal prostheses are generally formed astubular, radially-expandable stent-grafts. These stent-graft structureshave typically been formed with simplistic cylindrical frames or“stents”. A separate liner or “graft” is typically attached to the frameto prevent blood flow through a ruptured vessel wall. Such liners areoften formed from inelastic textiles to prevent pressure from distendinga weakened luminal wall. These branching textile liners have often beenwoven as continuous branching tubes to avoid any seams or joints whichmight fail after the stent-graft has been positioned. Unfortunately,this has also resulted in branch perimeters which are each a fraction ofthe perimeter of the liner at the common lumen, each branch typicallybeing half the common lumen in diameter. This does not accuratelyreflect the relative sizes of branching body lumens. Hence, somemismatch are inevitable when using the proportional branchingstent-grafts of the prior art.

[0008] Another problem associated with the branch stent-grafts of theprior art is that these known cylindrical structures generally formparallel branches when at rest, while the branches of body lumens oftenseparate at significant branching angles. Although it is possible todeform a straight branching prosthesis, the imposition of such axialbends on endovascular stent-grafts tends to cause folding and/orwrinkling which occlude their lumens and degrade their therapeuticvalue.

[0009] Still another disadvantage of known bifurcated stent-grafts isthat they often result in an imbalance in flow area to the differentbranches. Existing stent-grafts often rely, for at least some distance,solely on the liner material to maintain separation between branchinglumens. Such an external frame structure to support an internal flexibleliner, although effective at holding the total liner lumen open, doesnot provide a fixed separation between lumens. Instead, the linermaterial often pushes over to one side or the other. Although it ispossible to separate the lumens with a portion of the frame, compressionof such dual lumen frames is problematic, and would increase the totalcompressed diameter of branching prostheses.

[0010] For these reasons, it would be desirable to provide improvedbranching endoluminal prostheses, including stents and stent-grafts, andimproved methods for placement of such endoluminal prostheses to treataneurysms and other conditions. It would further be desirable to provideendoluminal prostheses which match the actual luminal geometries ofblood vessels and other body lumens without compromising theirtherapeutic effectiveness. It would be particularly desirable to provideadaptable prostheses and methods for their replacement which wouldfacilitate effective treatment of widely varying luminal systemgeometries without requiring an excessive inventory of prostheses tochoose from.

[0011] 2. Description of the Background Art

[0012] Copending U.S. patent application Ser. No. 08/538,706 (AttorneyDocket No. 16380-38), the full disclosure of which is herebyincorporated by reference, describes modular prostheses andconstructions methods which are particularly advantageous for use withthe bifurcated prostheses of the present invention.

[0013] U.S. Pat. No. 5,064,435 describes a self expanding prosthesiswhich maintains a stable axial length during expansion by anchoring ofradially outward flares at each end, and by sliding of an overlappingmedial region therebetween.

[0014] Vascular grafts and devices for their endoluminal placement aredescribed in U.S. Pat. Nos. 5,282,824; 5,272,971; 5,242,399; 5,219,355;5,211,658; 5,201,757; 5,192,297; 5,190,058; 5,158,548; 5,147,370;5,104,399; 5,092,877; 5,078,726; 5,019,085; 4,990,151; 4,950,227;4,913,141; 4,886,062; 4,820,298; 4,787,899; 4,617,932; 4,562,596;4,577,631; and 4,140,126; and European Patent Publications 539,237;533,511; 518,839; 518,704; 508 473; 505,686; 466 518; and 461 791.Catheters for placing vascular stents are described in U.S. Pat. Nos.5,192,297; 5,092,877; 5,089,005; 5,037,427; 4,969,890; and 4,886,062.Catheters carding a graft structure in a tube or capsule are describedin U.S. Pat. Nos. 5,275,622; 5,104,399; and 4,787,899; and EP466518.

SUMMARY OF THE INVENTION

[0015] The present invention provides branching modular intraluminaltubular prostheses, particularly stents and stent-grafts, for thetreatment of disease conditions, particularly aneurysms. Modularsections of the branching prostheses, or “prosthetic modules,” may beselectively combined to assemble a prosthesis having characteristicswhich are tailored to the specific requirements of the patient. Eachprosthetic module preferably includes one or more standard interfaceends for engaging another module, the module/module interface typicallycomprising ends which overlap and/or lock within a predetermined axialrange. Advantageously, the axial length, cross-section, perimeter,resilient expansive force, axial flexibility, liner permeability, linerextensibility, radial conformability, liner/tubal wall sealing andanchoring, and other prosthetic characteristics may be varied along theaxis of the assembled prosthesis, and also along the axis of eachprosthetic module. The modules are preferably individually introducedinto a lumen system of a patient body so that the prosthesis isassembled in situ. Ideally, selection of appropriate prosthetic modulesand the flexibility of the interface overlap range provides a custom fitintraluminal prosthesis which provides a therapy tailored to theindividual patient's needs.

[0016] The present invention provides endoluminal prosthetic structuresand methods which are particularly advantageous when applied withinmodular prosthetic therapies of the vascular system. Additionally,several aspects of the present invention will find use during otherendoluminal prosthetic procedures. Thus, intraluminal prostheses of thepresent invention are suitable for a wide variety of therapeutic uses,including stenting of the ureter, urethra, biliary tract, and the like.The present devices and methods will also be useful for the creation oftemporary or long term lumens, such as the formation of fistulas. Thepresent invention will find its greatest use, however, in the placementof endovascular prostheses into blood vessels for the treatment ofabdominal and other aneurysms, vascular stenoses, and the like.

[0017] In a first aspect, the present invention provides a branchingendoluminal stent-graft comprising a flexible liner over which aradially expandable frame is disposed. The flexible liner has a mainbody with a common lumen, and first and second branches having first andsecond branch lumens, the first and second branch lumens being incommunication with the common lumen. When expanded, the frame defines across-section having a first lobe supporting the first branch and asecond lobe supporting the second branch, and an isthmus therebetween.

[0018] Generally, two roughly opposed indentations are between the firstand second lobes, and an attachment mechanism attaches the first lobeand a portion of each indentation to the first branch. Similarly, theattachment mechanism also attaches the second lobe and an alternateportion of each indentation to the second branch. Thus, both the lobesand indentations help to support the liner lumens in an openconfiguration when the frame is expanded, while the indentation alsoprovide separation between the lumens. As the frame cross-section isgenerally contiguous, the frame itself having only a single structurallumen, radial compression of the frame to a small diameter for insertionand positioning within the body lumen system is not compromised.

[0019] In another aspect, the present invention provides a branchingendoluminal stent-graft comprising a radially expandable tubular frameand a flexible inelastic liner supported by the frame. The liner has amain body with a common lumen, and first and second branches extendingfrom the body having first and second branch lumens, respectively. Thesefirst and second branch lumens are in communication with the commonlumen, and a perimeter of the common lumen is smaller than a sum of theperimeter of the first branch lumen and a perimeter of the second branchlumen. Preferably, the sum of the first and second branch lumenperimeters is between 1% and 20% more than the common lumen perimeter.This structure promotes anatomical matching of the prosthesis withbranching body lumen systems, particularly with the abdominal aorta andiliac arteries for the treatment of abdominal aneurysms. Advantageously,the liner often comprises a continuously woven tube to avoid the dangersassociated with seams or the like. Conveniently, the liner may beselectively shrunk, or may alternatively be plastically expanded, toprovide the anatomically matched perimeters of the present invention.

[0020] In yet another aspect, the present invention provides an angledbranch endoluminal prosthesis comprising a radially expandable tubularmain body having a common lumen and a radially expandable tubular firstbranch extending from the main body. The first branch has a first branchlumen in fluid communication with the common lumen when the prosthesisis expanded. Similarly, a radially expandable tubular second branchextends from the main body, and has a second branch lumen in fluidcommunication with the common lumen when the prosthesis is expanded. Thecommon lumen and the first branch lumen define a first open flow pathhaving a preset first branch angle in the range between 15° and 90° whenthe prosthesis is expanded. Typically, the common lumen and the secondbranch lumen will also define a second open flow path having a presetsecond branch angle in the range between 15° and 90°. Preferably, thefirst and second branch angles will be in the range between 30° and 45°.These preset branch angles match the common branching angles of theiliac arteries from the abdominal aorta, thereby improving flow throughprostheses used in the treatment of abdominal aneurysms.

[0021] Oftentimes, the angled branch prostheses of the present inventionwill comprise resilient structures which form the preset bend angle whenat rest. Hence, once the prosthesis is implanted, axial bending of theprosthesis by the surrounding tissues is minimized, reducing wrinklingand folding of the lumen. Such a structure also avoids the imposition ofstraightening forces against weakened vessel tissues. In a particularlyadvantageous embodiment, the liner comprises a corrugated region toincrease the local axial flexibility of the prosthesis, and to allow theprosthesis to adapt to a range of branch angles.

[0022] In another aspect, the present invention provides an angledprosthetic module comprising a radially expandable tubular body portionhaving a bend and a lumen. The lumen provides an open flow path when thebend defines a preset angle in the range between 15° and 90°. A standardinterface is disposed on an end of the body portion, the standardinterface fittingly engagable with any of a plurality of standardinterface ends of other endoluminal prosthetic modules. Generally, thebend has a preset radial orientation and the prosthesis furthercomprises a rotational marker disposed on the body or interface end.Such rotational markers, typically being visible under fluoroscopy,greatly facilitate alignment of the preset radial orientation of theprosthesis with a bend in the body lumen.

[0023] In yet another aspect, the present invention provides anendoluminal prosthesis kit comprising an expandable tubular Y-connectormodule having a common lumen, a first branch lumen, and a second branchlumen, the first and second branch lumens being in communication withthe common lumen. At least one of the common lumen, the first branchlumen, and the second branch lumen have an associated first standardinterface end. A plurality of alternative radially expandable prostheticmodules are associated with each standard interface end. Each of thealternative modules has a tubular body portion and a. second interfaceend. Each associated interface end is fittingly engagable with the firstinterface end, and the plurality of alternative body portions providedifferent selectable assembled prosthetic characteristics. Generally,the alternative body portions will differ in at least of length,cross-section, taper, bend angle, axial flexibility, exterior fiberprotrusion, liner permeability, liner extensibility, radialconformability, or resilient radial spring force. In a particularlypreferred embodiment, the first and second interface ends overlap withina predetermined range when engaged. This overlap range allows the totalaxial length of the assembled prosthesis to be tailored to theparticular patient's needs.

[0024] In yet another aspect, the present invention provides anendoluminal prosthetic Y-connector module comprising a radiallyexpandable body portion having a common lumen, a first branch lumen, anda second branch lumen, the first and second branch lumens being incommunication with the common lumen. At least one standard interface endis disposed on the body portion adjacent to at least one of the commonlumen, the first branch lumen, and the second branch lumen. Eachstandard interface end is fittingly engagable with any of an associatedplurality of standard interface ends of other endoluminal prostheticmodules having differing prosthetic characteristics.

[0025] In yet another aspect, the present invention provides a markedstent-graft comprising a radially expandable tubular frame, a flexibleliner supported by the frame, and an attachment mechanism which holdsthe liner on the frame. Markers are disposed on at least one of theframe, the liner, and the attachment mechanism. The markers are visibleunder imaging to indicate the axial and/or rotational position of thestent-graft.

[0026] As used herein, “visible under imaging” means an element which isvisible under fluoroscopy, ultrasound, or other imaging modalities, soas to define an identifiable shape which is distinguishable from theadjacent structural elements and the surrounding body tissues.Preferably, the markers indicate position both while the prosthesis isin a compressed mode, as is typically used during insertion, and alsowhile the prosthesis is in the expanded mode after it has been deployed.The marker thereby facilitate positioning of the prosthesis, and alsoallows continuing verification of the position of the deployedprosthesis relative to the body tissues. Finally, such markers may alsobe used to position additional prosthetic modules relative to theexpanded prosthesis.

[0027] The present invention further provides a method for placement ofstent-grafts comprising inserting a branching stent-graft into a patientbody and positioning the branching stent-graft at a target locationwithin a body lumen. The branching stent-graft comprises a tubular frameand a flexible liner having a main body with a common lumen. Thestent-graft is expanded at the target location, and the liner issupported at a cross-section by the frame so that the common lumen isheld in open. At a second cross-section, a first lobe of the frame holdsa first lumen of the liner open, and a second lobe of the frame holds asecond lumen of the liner open. An isthmus of the frame disposed betweenthe first lobe and the second lobe separates the first lumen from thesecond lumen. This separation of the lumens is particularly beneficialwhen a tubular branch prosthesis is inserted into, and expanded within,either the first or second lumen, as it maintains the intended balancebetween the branching luminal flows.

[0028] In another aspect, the present invention provides a method forplacement of a branching endoluminal stent-graft comprising inserting abranching stent-graft into a patient body, and positioning the branchingstent-graft at a target location within a body lumen. The branchingstent-graft is expanded at the target location, the branchingstent-graft comprising a tubular frame and an inelastic liner. The lineris held in an open configuration by the frame so that a perimeter of acommon lumen of the liner is smaller than a sum of a perimeter of afirst branch lumen of the liner and a perimeter of a second branch lumenof the liner, thereby anatomically matching branching body lumengeometries.

[0029] In yet another aspect, the present invention provides a methodfor treating a bent target region of a body lumen,. the methodcomprising inserting an endoluminal prosthesis into the body lumen in aradially compressed configuration. The prosthesis has a bend defining apreset angle when in an expanded configuration. The prosthesis ispositioned at the bent target region, and the preset angle isrotationally aligned with the bent target region. The aligned prosthesisis then expanded at the bent target region, thereby avoiding any kinkingor wrinkling of the prosthesis lumen, and avoiding straightening loadsimposed by the prosthesis on the surrounding body lumen.

[0030] In yet another aspect, the present invention provides a method ofproducing a branching stent-graft comprising providing a flexibletubular liner having a main body, a first branch extending from the mainbody, and a second branch extending from the main body. At least aportion of the main body is selectively shrunk relative to at least oneof the first branch and the second branch. A radially compressible frameis attached to the tubular liner. Typically, a perimeter of the mainbody portion is shrunk by up to 20% relative to a perimeter of at leastone of the first branch and the second branch.

[0031] In yet another aspect, the present invention provides a methodfor producing a branching endoluminal prosthesis, the method comprisingfabricating a resilient tubular frame and expanding the frame to anexpanded configuration. The expanded frame is then heat-treated whilebeing restrained with a cross-section that defines two lobes separatedby at least one indentation. A flexible liner is attached to a firstlobe and an adjacent portion of the at least one indentation, so that afirst lumen of the liner is held open by the frame.

[0032] In yet another aspect, the present invention provides a modularendoluminal prosthesis placement method comprising inserting aY-connector prosthetic module within a body lumen system, andpositioning a main body of the Y-connector prosthetic module at a targetlocation adjacent to first and second branch lumens of a body lumensystem. The first prosthetic module is radially expanded at the targetlocation. A preferred first branch prosthetic module is selected from aplurality of alternative branch prosthetic modules, and an end of thepreferred first branch prosthetic module is positioned adjacent to thefirst branch of the body lumen system. The preferred first branchprosthetic module is radially expanded, and once expanded, engages theY-connector prosthetic module.

[0033] In yet another aspect, the present invention provides a methodfor assembling endoluminal prosthetic modules within a body lumen, themethod comprising deploying a first prosthetic module within the bodylumen, and inserting a second tubular prosthetic module into the bodylumen in a radially compressed configuration. Markings disposed on atleast one of the first and second prosthetic module are imaged, and animage of the markings is aligned with an image of the other of the firstprosthetic module and the second prosthetic module. An end of thealigned second prosthetic module is then expanded to engage an end ofthe first prosthetic module.

[0034] In a final aspect, the present invention provides a method forpositioning endoluminal prosthetic modules within a body lumen, themethod comprising inserting a tubular prosthesis into the body lumen ina radially compressed configuration. Markings disposed upon the insertedprosthetic module are imaged, and an asymmetric marker element isrotationally oriented, thereby providing a rough rotational alignment ofthe prosthesis. The image of marker elements disposed at differentradial locations about the prosthesis may then be brought together toprecisely rotationally align the prosthesis within the body lumen.Finally, the aligned prosthesis may then be expanded within the bodylumen.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035]FIG. 1 is a side view of an exemplary cylindrical vascular grafthaving axially constant characteristics.

[0036]FIG. 2 is a perspective view of an exemplary delivery catheter foruse with the prostheses of the present invention, with a portion of thedistal end broken away to disclose a prosthesis therein.

[0037]FIGS. 3 and 3A illustrate a branching endoluminal prosthesisassembled from a plurality of prosthetic modules according to theprinciples of the present invention.

[0038]FIG. 4 is a schematic illustration of a modular branchingprosthesis kit, according to the principles of the present invention.

[0039]FIG. 5 illustrates a preferred prosthetic Y-connector modulestructure having a branching flexible liner which is supported by aradially expandable frame including two lobes separated by opposedindentations, for use with the modular prothesis kit of FIG. 4.

[0040] FIGS. 5A-C illustrate cross-sections along the axis of theY-connector prosthetic module of FIG. 5.

[0041]FIG. 5D illustrates a method for producing the lobed cross-sectionof the Y-connector prosthetic module of FIG. 5.

[0042]FIG. 6 illustrates an angled branch endoluminal prosthesis havinga preset branch angle, according to the principles of the presentinvention.

[0043] FIGS. 6A-B illustrate a method for producing a prebent liner foruse in the angled branch prosthesis of FIG. 6.

[0044] FIGS. 6C-E illustrate a corrugated liner having a preset branchangle, and which maintains an open flow path within a range of branchangles, for use in the angled branch endoluminal prosthesis of FIG. 6.

[0045]FIG. 7 is an exploded view of a branching endoluminal prosthesisassembled from position-indicating prosthetic modules having overlapindicators according to the principles of the present invention.

[0046] FIGS. 8-8B illustrate alternative embodiments of endoluminalprostheses having rotational markers, including both asymmetric elementsand alignable elements at differing radial positions.

[0047] FIGS. 9-9C illustrate an exemplary method for assemblingprosthetic modules into a branching endoluminal prosthesis in situwithin a branching body lumen system, according to the principles of thepresent invention.

[0048]FIG. 10 illustrates an alternative branching endoluminalprosthesis assembled from prosthetic modules, including modules havinghighly flexible sections along which a liner is supported by helicalwindings, according to the principles of the present invention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

[0049] The present invention will find its greatest use as anendovascular prostheses for the treatment of diseases of thevasculature, particularly aneurysms, stenoses, and the like. Theprostheses will generally be radially expandable from a narrow-diameterconfiguration to facilitate introduction into the body lumen, typicallyduring surgical cutdown or percutaneous introduction procedures.Exemplary delivery catheters and methods for placement of the prosthesesof the present invention are more fully described in copending U.S.patent application Ser. No. 08/475,200, (Attorney Docket No.16380-11-3), the full disclosure of which is incorporated herein byreference.

[0050] An exemplary cylindrical graft structure 10 is illustrated inFIG. 1. Prosthesis 10 comprises a perforate tubular frame 12 whichincludes a plurality of independent (non-connected) ring frames 14. Thetubular frame 12 supports an inner liner 18. Optionally, an outer lineris disposed over the ring frames, either instead of inner liner 18, orin combination therewith.

[0051] To secure ring frames 14 in place, and to secure the liner to theperforate tubular frame 12, the liner is typically sutured to the frame.A wide variety of alternative liner/frame attachment mechanisms areavailable, including adhesive bonding, heat welding, ultrasonic welding,and the like. Where inner and outer liners are used, the ring frames maybe sandwiched between the liners and held in place by attaching theliners to each other.

[0052] The prosthesis 10 will typically have a length in the range fromabout 20 mm to 500 mm, preferably from 50 mm to 200 mm, with a relaxeddiameter in the range from about 4 mm to 45 mm, preferably being in therange from 5 mm to 38 mm.

[0053] Referring now to FIG. 2, an exemplary delivery catheter 30 foruse with the endoluminal prostheses of the present invention comprises atubular cover 32 and a shaft 34. Cover 32 has a central lumen 36extending from a proximal end 38 to a distal end 40. Shaft 34 isslidably received within central lumen 36 and extends proximally ofcover 32.

[0054] A plurality of runners 42 extend distally from shaft 34. Runners42 line a portion of the inner surface of lumen 36, and slide within thelumen with the shaft. Shaft 34 also has a lumen, in which a core shaft44 is slidably disposed. Core shaft 44 has a guide wire lumen 46.Nosecone 48 is fixed to the distal end of core shaft 44, and cantherefore be manipulated independently of runners 42.

[0055] Prosthesis 10 is radially compressed and restrained within theplurality of runners 42. In turn, cover 32 prevents runners 42 fromexpanding outward. Runners 42 are formed from a hard material, anddistribute the expansion load of prosthesis 10 over the inner surface ofcentral lumen 36. The deploying force is applied proximally against aslider 50 attached to distal end 38 of cover 30, while holding a luerfitting 52 at the distal end of shaft 34, thereby withdrawing the coverproximally from over the prosthesis. An additional luer adaptor 54 atthe distal end of core shaft 44 allows the core shaft to be manipulatedindependently, and to be releasably secured to the shaft 34.

[0056] Referring now to FIGS. 3 and 3A, a branching endoluminalstent-graft 60 is assembled from prosthetic modules selected to matchthe needs of the diseased vascular system of the patient. A common lumencuffed prosthetic module 62 seals and anchors the assembled prosthesisin the body lumen, typically within the abdominal aorta below the renalarteries and above the left and right iliac arteries. Y-connector module64 engages cuffed common lumen module 62, and separates the blood flowfor the iliac arteries. First angled branching prosthetic module 66 andsecond angled branching prosthetic module 68 engage the branch lumens ofY-connector module 64 to direct the luminal flow along first and secondbranching body lumens.

[0057] The modular construction of branching prosthesis 60 allowsindividual tailoring of the common lumen, first branch lumen, and secondbranch lumen to match the geometry of the body lumen system. Forexample, a perimeter of common lumen cuffed module 62 may be selectedindependently of the branching lumen perimeters. Specifically, theperimeter of the abdominal aorta is typically as much as 20% less thanthe sum of the perimeters of the iliac arteries. Preferably, theserelative luminal proportions are reflected in Y-connector module 64,ideally by selective shrinking of a flexible liner, wherein theY-connector comprises a stent-graft. Selective shrinking of stent-graftliners is fully explained in copending U.S. patent application Ser. No.08/538,706 (Attorney Docket 16380-38), the full disclosure of which haspreviously been incorporated herein by reference.

[0058] The cross-sectional shape of Y-connector module 64 isparticularly advantageous for use in modular the modular endoluminalprostheses of the present invention. The cross-section adjacent thebranches includes individual lobes which receive the first and secondbranch modules 66, 68, and also includes an isthmus 65 between theselobes to maintain a fixed separation between the branches. Additionally,as illustrated in FIG. 3C and described hereinbelow, the lobes andindentations defining isthmus 65 increases the area available for suture63 or other frame/liner attachment mechanisms.

[0059] Referring now to FIG. 4, a branching endoluminal prosthesis kit70 includes a plurality of alternative selectable common lumen modules72 which vary in diameter, length, or other prosthetic characteristics.Each of common lumen modules 72 interchangeably engages branching module74. Branching module 74 comprises a Y-connector module having a singleextended branch, thereby minimizing the number of joints and theprosthesis positioning and assembly time, while still allowingvariability between the two branches and the common lumen end. Aplurality of second branch prosthetic modules 76 provide variations indiameter, length, preset bending angle, and the like. These secondbranch prosthetic modules may optionally include cuffed ends, or mayalternatively be engagable by still further prosthetic modules.

[0060] A particularly advantageous structure for use in a branchingendoluminal Y-connector will be described with reference to FIG. 5.Y-connector module 64 comprises a radially expandable frame 80supporting a liner 82. Frame 80, in turn, comprises a plurality of ringframes 78 which are interconnected by bridges 84. Frame 80 thereforeforms a fairly stiff structure, particularly when liner 82 is attachedto a malleable frame. Alternatively, frame 80 may be formed as a seriesof independent, frame rings to increase the axial flexibility of theY-connector module. Such independent frame rings may be resilient,malleable, or both.

[0061] Liner 82 of Y-connector module 64 includes a main body 86 and aseptum 88. As is seen most clearly in FIGS. 5A-C, the liner along mainbody 86 defines a single common lumen 90. Along septum 88, the linerdefines a first branch lumen 92 and a second branch lumen 94. The firstand second branch lumens 92, 94 may be entirely separate, but arepreferably interconnected along center line 96 to help hold the liner inan open configuration. The liner is preferably formed as a continuouswoven tube, thereby avoiding seams and/or joints which might fail afterplacement. Ideally, the liner comprises a woven polyester such Dacron™,which has been selectively shrunk to match the anatomical lumengeometries.

[0062] As is most clearly seen in FIG. 5C, a cross-section of frame 80adjacent to the septum of the liner defines a contiguous cross-sectionhaving a first lobe 98, a second lobe 100, and opposed indentations 102to support and separate the first and second branches of the liner. Thecontiguous nature of the frame facilitates compression of the frame byavoiding frame internal crossing elements, while the lobes andindentations increase the attachment area between each liner branch andits associated portion of the frame.

[0063] The lobes and indentations further ensure that the flow betweenthe two branches will remain even by substantially separating the septumof the liner into distinct flow areas. This is particularly importantwhere prosthetic branch modules will be inserted into the septum, as theexpansion of such branch modules within the septum would tend to push anunsupported liner to one side, resulting in an uneven flow. Thisinteraction can be understood with reference to FIG. 3, where firstbranch module 66 has been inserted farther into the septum than secondbranch module 68. If the flexible liner alone were relied upon tomaintain distribution between the branches, the inserted end of firstbranch module 66 may well push the liner barrier into the flow regionintended for the second branch of the body lumen.

[0064] Referring now to FIG. 5D, the preferred method for imposing theseparated lobed cross-section on Y-connector frame 80 comprisessupporting the frame on a jig having lobe dowels 106 and indentationdowels 108. While the frame is supported on the jig, the frame isheat-treated, resiliently biasing the frame toward the lobedcross-section. Typically, the frame will be formed from a biocompatiblehigh-strength alloy such as stainless steel, platinum, or the like,ideally comprising a shape-memory alloy such as Nitinol™.

[0065] Although the preferred frame structure has been described withreference to a Y-connector module, thereby taking advantage of themodular prosthesis construction of the present invention, the lobedframe structure will be advantageous for any branching endoluminalstent-graft, as it maintains each lumen of the liner in an openconfiguration by supporting the liner along a greater proportion of itsperimeter, but without compromising the radial compressibility of thetotal stent-graft.

[0066] Referring now to FIGS. 6-6B, a preferred angled branchstent-graft 110 includes a common lumen 112 and a first branch 114 whichforms a branch angle a relative to the common lumen portion 112 when theprosthesis is at rest. It has been found that the abdominal aorta andiliac arteries define angles of between 15° and 90°, more commonlybetween 30° and 45°. While the endoluminal prostheses of the prior arthave been designed to allow some axial bending, imposition of suchangles often leads to kinking and/or wrinkling of the liners of knownendoluminal stent-grafts. The prostheses of the present invention aretypically straightened and radially compressed during insertion, butwill form the preset bend angle a when expanded and in a relaxed state.

[0067] While a frame 116 may be biased to form an angle α without aprebent liner, the open flow path through the bent prosthesis lumen isgreatly improved by preforming liner 118 to accept the bentconfiguration. As illustrated in FIGS. 6AB, prebent liner 118 may beformed simply by folding and stitching inner bend region 120.Optionally, the excess material may be removed. Although such a methodis effective at setting a specific prebend angle α, the sharp bend inthe branch lumen will still impede luminal flow somewhat, and wrinklingand/or kinking may result if there is a significant mismatch between thebend angle of the prosthesis and the bend angle of the body lumen.

[0068] Referring now FIGS. 6C-E, a preferred prebent liner 122 includesa corrugated joint 124. Such a corrugated liner will typically also havea prebend angle, but will adapt to a much wider range of branch angleswithout excessively occluding the branch lumen flow. Formation of such acorrugation region is fully described in copending U.S. patentapplication Ser. No. 08/538,706 (Attorney Docket 16380-38), the fulldisclosure of which has previously been incorporated herein byreference.

[0069] Referring now to FIG. 7, a modular position-indicating branchedstent-graft 130 comprises a marked Y-connector 132 and marked branchmodules 140. Marked Y-connector 132 includes a main body 134 and aseptum 136 as described above. Overlap marker bands 138 provide a brightcontrast under fluoroscopy, ultrasound, or other imaging modalities, toensure that the marked Y-connector and marked branch modules overlapwithin a predetermined range. Were the overlap allowed to exceed thatpredetermined range, the branch prosthesis module would extend into themain body portion of the Y-connector module, where it is no longersupported by the septum frame, and where it might therefore fold overand block flow into either or both branches. Were the overlapinsufficient, the branch and Y-connector modules may become separated,allowing blood to flow through a ruptured aneurysm.

[0070] In the embodiment shown, the overlap is within the range so longas the branch marker band image is between and separate from the markerbands of the septum. The use of an overlap-indicating delivery system toprovide similar safety benefits was described in copending U.S. patentapplication Ser. No. 08/475,200 (Attorney Docket 16380-11-3), the fulldisclosure of which is incorporated herein by reference.

[0071] It is particularly advantageous to provide marker bands which arevisible while the prosthetic modules are radially compressed forinsertion and positioning, and which are also visible once the modulesare fully expanded and interlocked, thereby allowing module positioningand verification of the assembled prosthesis. The preferred markers willtherefore expand with the prosthesis, but will not add significant bulkso as to impede radial compression. Optionally, tantalum, platinum,gold, tin, or the like may be coated onto the frame in selected areas toprovide a radio opaque marker. Alternatively, metal wire might bewrapped around selected portions of the frame or woven into the liner.Although such methods are fairly effective, they are generallylabor-intensive, bulky, and do not provide the bright, continuous,clearly defined image which is desired.

[0072] In a particularly preferred embodiment, marker bands and otherposition-indicating elements may be applied directly to the flexibleliner material as a radio opaque paste or paint. Such a paste may beprepared by mixing tantalum powder with a polyester in a suitablesolvent, such as hexafluoro-2 propanol. This radiopaque paste may thenbe painted onto a woven Dacron™ or other suitable liner in the desiredshapes. The relative proportions of the materials may be varied toprovide the desired image density and adhesion qualities.

[0073] Referring now to. FIG. 8, the angled prostheses of the presentinvention will often be formed with a bend at a specific rotationalorientation. It is therefore highly advantageous to provide markingelements which provide an indication of the rotational orientation ofthe prosthesis to facilitate the alignment of the prosthetic bend withthe bends of the body lumen system. Rotational-indicating angleprosthesis 150 includes alignable marker elements 152 and an asymmetricmarker element 154.

[0074] The asymmetric element 154 indicates the general orientation ofthe prosthesis during positioning. The precise rotational alignment ofthe prosthesis is then provided by aligning the image of alignableelements 152 with the asymmetric element 154, these elements beingsituated at different axial positions about the tubular prosthesis. Byfirst positioning the fluoroscopic, ultrasound, or other imagingmechanism in the proper orientation relative to the body lumen, and bythen aligning the marker elements of the prosthesis relative to thatorientation, very precise rotational alignment of the prosthesis can beachieved.

[0075] Referring now to FIGS. 8A-B, a rotational-indicating Y-connectormodule 160 includes a vertical marker bar 162 and horizontal alignmentbars 164. These elements are again disposed at differing radialpositions about the prosthesis, providing precise angular alignment ofthe prosthesis through alignment of the marker element images. In thisembodiment, the marker elements align to form the asymmetric angularposition indicator 166, here forming the letter “E”.

[0076] Clearly, a wide variety of alternative rotational indicatormarkers might be used. Nonetheless, the combination of an asymmetricmarker to prevent misalignment of the prosthesis by 180°, in combinationwith alignable elements at differing radial positions to provide preciseangular alignment is preferred for prostheses which do not have an axialplane of symmetry.

[0077] The in situ assembly of the modular bifurcated prostheses of thepresent invention may be understood with reference to FIGS. 9-9C.Abdominal aneurysm AA is located below the renal arteries R and extendsdown into at least one of the iliac arteries I1, I2. A cuffedendoluminal prosthetic module 170 having marker bands 172 at either endis inserted with an inferior approach and positioned using deliverycatheter 30. Marker bands 172 help to position cuffed module 170 at atarget location below the renal arteries, with a majority of theprosthesis adjacent to the healthy luminal wall of the aorta A.

[0078] Once the module is at the target location, cuffed module 170 isexpanded. Typically, the module expands resiliently as the deliverycatheter cover is removed. Ideally, an expansible liner is thenplastically expanded by balloon catheter 174 to match the prosthesisperimeter to that of the surrounding aorta, as shown in FIG. 9A, and asmore fully explained in copending application Ser. No. 08/538,706(Attorney Docket No. 16380-38).

[0079] Once the cuffed module is in place, position-indicatingY-connector module 180 is then inserted and positioned within the lowerend of cuffed module 170. Overlap indicators 182 are positioned oneither side of marker band 172 to ensure that the overlap is within thepredetermined range. The prosthesis is rotated until alignable elements184 are vertically aligned. As this Y-connector module is formed withsymmetric branches, no asymmetric element is required. Alternatively, aY-connector module having one integral branch might be used, in whichcase an asymmetrical element would prevent misalignment of the openbifurcated lumen. Otherwise, misalignment or crossing of the branchesmight seriously occlude flow through one or both branch lumens.

[0080] The overlapped interface ends of the cuffed module and theY-connector module may optionally be “locked” together by plasticallyexpanding the inner interface end with balloon catheter 174. Preferably,the outer interface end of the cuffed module includes a non-distensibleliner to avoid stressing the body lumen, while the Y-connector interfaceend comprises a plastically expansible liner such as a partiallyoriented yarn. Such locking of the overlapped modules helps ensure thatthe joints remain fixed once proper positioning has been completed.

[0081] First angled branch prosthetic module 190 is next positionedwithin the septum of the Y-connector module 180. Marker band 172 isagain positioned between the overlap indicators 182 (not shown in FIG.9C for clarity), while the preset radial orientation of the branch anglebend is indicated by asymmetric element 192. The visibility of thevarious position-indicator markers prior to expansion of the prosthesescan be seen to facilitate positioning of the prostheses using deliverycatheter 30. Additionally, their continued visibility on the prostheticmodules helps to ensure continued alignment of the various modules asassembly proceeds.

[0082] Referring now to FIG. 10, a highly flexible prosthesis is againassembled from a plurality of prosthetic modules, including Y-connectormodule 64, a flexible common lumen module 202, and first and secondbranch modules 204, 206. Each of flexible modules 202, 204, and 206comprise a highly flexible section including a flexible liner material208 which is supported by a frame comprising at least one spiral member210. Such a spiral structure will hold the liner open radially, and willalso provide some axial support, but will generally not substantiallyincrease the axial stiffness, allowing the prosthesis to adapt to thehighly tortuous branching paths which often occur with aneurysms.Preferably, one or two spiral members are used to maximize axialflexibility. Where two spiral members are included, they may becounterwound.

[0083] The ends 212 of flexible modules 202, 204, and 206 opposite-theY-connector module preferably include anchoring frames, ideallycomprising resilient cuffs to seal against the surrounding lumenal wall,as described above. Ring frame sections may also be incorporated intothe ends of the flexible modules which engage the Y-connector structureto provide sealing and prevent relative movement of the modules.Finally, it should be recognized that the Y-connector and the commonlumen module and/or one of the branch modules may be produced as asingle unit, so that only a single branch is a assembled in situ. Infact, such spirally supported intermediate flexible prosthetic sections,for use between anchoring frame sections, need not be limited to modularprostheses.

[0084] While the foregoing has been described in some detail, forpurposes of clarity and understanding, certain changes and modificationswill be obvious to those of skill in the art. Thus, the scope of thepresent invention is limited solely by the appended claims.

What is claimed is:
 1. A branching endoluminal stent-graft comprising: aflexible liner having a main body with a common lumen, a first branchhaving a first branch lumen, and a second branch having a second branchlumen, the first and second branch lumens being in communication withthe common lumen; and a radially expandable frame disposed over at leasta portion of the liner, the frame defining a frame lumen cross-sectionhaving a first lobe supporting the first branch, a second lobesupporting the second branch, and at least one isthmus therebetween. 2.A stent-graft as claimed in claim 1, wherein the isthmus is defined bytwo roughly opposed indentations between the first and second lobes. 3.A stent-graft as claimed in claim 2, further comprising an attachmentmechanism which attaches the first lobe and a portion of each indentionto the first branch.
 4. A stent-graft as claimed in claim 3, wherein theattachment mechanism also attaches the second lobe and an alternateportion of each indentation to the second branch.
 5. A stent-graft asclaimed in claim 3, wherein the attachment mechanism comprisesstitching.
 6. A stent-graft as claimed in claim 1, wherein the framecomprises an axially continuous perforate tubular structure extendingover at least a portion of both the main body and the first and secondbranches.
 7. A stent-graft as claimed in claim 6, wherein the tubularstructure comprises a malleable material.
 8. A stent-graft as claimed inclaim 1, wherein the frame comprises a plurality of independent framerings.
 9. A stent-graft as claimed in claim 8, wherein a plurality ofthe frame rings comprise a resilient material.
 10. A branchingendoluminal stent-graft comprising: a radially expandable tubular frame;and a flexible, inelastic liner supported by the frame, the liner havinga main body with a common lumen, a first branch having a first branchlumen, and a second branch having a second branch lumen, the first andsecond branches extending from the main body, the first and secondbranch lumens being in communication with the common lumen, and aperimeter of the common lumen being smaller than a sum of a perimeter ofthe first branch lumen and a perimeter of the second branch lumen.
 11. Abranching stent-graft as claimed in claim 10, wherein the sum of thefirst and second branch lumen perimeters is in the range between 1 and20% more than the common lumen perimeter.
 12. A branching stent-graft asclaimed in claim 10, wherein the frame comprises a resilient structure.13. A branching stent-graft as claimed in claim 10, wherein the linercomprises a continuously woven textile tube.
 14. A branching stent-graftas claimed in claim 13, wherein at least a portion of the liner whichdefines the common lumen perimeter has been selectively shrunk relativeto one of the first and second branch lumen perimeters.
 15. A branchingstent-graft as claimed in claim 14, wherein the liner comprises apolyester.
 16. A branching stent-graft as claimed in claim 10, whereinat least a portion of the liner which defines the first and secondbranch lumen perimeters has been selectively plastically expanded.
 17. Abranching stent-graft as claimed in claim 16, wherein the liner has beenexpanded in situ to match a branching body lumen.
 18. An angled branchendoluminal prosthesis comprising: a radially expandable tubular bodymain body having a common lumen; a radially expandable tubular firstbranch extending from the main body, the first branch having a firstbranch lumen in fluid communication with the common lumen when theprosthesis is expanded; and a radially expandable tubular second branchextending from the main body, the second branch having a second branchlumen in fluid communication with the common lumen when the prosthesisis expanded; wherein the common lumen and the first branch lumen definea first open flow path having a preset first branch angle in the rangebetween 15° and 90° when the prosthesis is expanded.
 19. An angledbranch prosthesis as claimed in claim 18, wherein the common lumen andthe second branch lumen define second open flow path having a presetsecond branch angle in the range between 15° and 90° when the prosthesisis expanded.
 20. An angled branch prosthesis as claimed in claim 19,wherein the first and second branch angles are in the range between 30°and 45°.
 21. An angled branch prosthesis as claimed in claim 18, whereinat least one of the main body, the first branch and the second branchcomprises an expandable perforate frame supporting a flexible liner, andwherein the frame comprises a resilient material and the first flow pathdefines the first branch angle when the prosthesis is at rest.
 22. Anangled branch prosthesis as claimed in claim 21, wherein the linercomprises a corrugated region.
 23. An angled prosthetic modulecomprising: a radially expandable tubular body portion having a bend anda lumen, the lumen providing an open flow path when the bend defines apreset angle in the range between 15 and 90; and a standard interfacedisposed on an end of the body portion, the standard interface fittinglyengagable with any of a plurality of standard interface ends of otherendoluminal prosthetic modules having differing prostheticcharacteristics.
 24. An angled prosthetic module as claimed in claim 23,wherein the lumen provides the open flow path when the angle is in therange between 30° and 45°.
 25. An angled prosthetic module as claimed inclaim 23, wherein the bend has a preset radial orientation, and furthercomprising a rotational marker disposed on at least one of the body andthe interface end.
 26. An angled prosthetic module as claimed in claim23, wherein the body comprises an expandable perforate frame supportinga flexible liner, wherein the frame comprises a resilient material, andwherein the open flow path defines the angle when the prosthesis is atrest.
 27. An angled prosthetic module as claimed in claim 23, whereinthe body comprises an expandable perforate frame supporting a flexibleliner, and wherein the liner comprises a corrugated region.
 28. Anendoluminal prosthesis system comprising: an expandable tubularY-connector module having a common lumen, a first branch lumen, and asecond branch lumen, the first and second branch lumens being incommunication with the common lumen; and a plurality of radiallyexpandable prosthetic modules, each module having a tubular body portionand an end which fittingly engages at least one of the common lumen, thefirst branch lumen, and the second branch lumen; wherein the pluralityof body portions provide different selectable assembled endoluminalprosthetic characteristics.
 29. A prosthesis system as claimed in claim28, wherein the plurality of body portions differ in at least oneprosthetic characteristic selected from the group consisting of length,cross-section, taper, bend angle, axial flexibility, exterior fiberprotrusion, liner permeability, liner extensibility, radialconformability, and resilient radial spring force.
 30. A prosthesissystem as claimed in claim 29, wherein at least two of the plurality ofbody portions differ in cross-section.
 31. A prosthesis system asclaimed in claim 28, wherein the plurality of the prosthetic moduleshave ends which are alternatively fittingly engagable with a branchlumen interface end of the Y-connector module, and wherein at least twoof the plurality of alternative prosthetic modules have body portionswhich provide different preset branch angles from the common lumen, thebranch angles in the range between 15° and 90°.
 32. A prosthesis systemas claimed in claim 31, wherein the preset bend angles have a presetradial orientation, and wherein each of the at least two alternativeprosthetic modules include rotational markers visible under imaging toindicate the preset radial orientation.
 33. A prosthesis system asclaimed in claim 28, wherein engagement of the end of each prostheticmodule with the Y-connector module affixes the prosthetic module and theY-connector module with an axial overlap, the overlap being within apredetermined range.
 34. A prosthesis kit as claimed in claim 33,wherein at least one of the Y-connector module and each prostheticmodule comprise markers visible under imaging to indicate thepredetermined range of overlap.
 35. An endoluminal prostheticY-connector module comprising: a radially expandable body portion havinga common lumen, a first branch lumen, and a second branch lumen, thefirst and second branch lumens being in communication with the commonlumen; and at least one standard interface end disposed on the bodyportion adjacent to at least one of the common lumen, the first branchlumen, and the second branch lumen, each standard interface end beingfittingly engagable with any of an associated plurality of standardinterface ends of other endoluminal prosthetic modules having differingprosthetic characteristics.
 36. A Y-connector module as claimed in claim35, wherein the at least one standard interface comprises both a firstbranch lumen standard interface and a common lumen branch interfacewhich is different than the first branch interface.
 37. A Y-connectormodule as claimed in claim 36, further comprising a second branchinterface disposed at another of the common lumen, the first branchlumen, and the second branch lumen.
 38. A Y-connector module as claimedin claim 35, further comprising markers visible under imaging on atleast one of the body portion and a marked interface end.
 39. AY-connector module as claimed in claim 38, wherein the markings comprisea flexible radiopaque material disposed on the liner.
 40. A Y-connectormodule as claimed in claim 38, wherein the markers comprise an overlapindicator to facilitate overlapping prosthetic modules within apredetermined range.
 41. A Y-connector module as claimed in claim 38,wherein the markers comprise a rotational indicator.
 42. A Y-connectormodule as claimed in claim 41, wherein the rotational indicatorcomprises alignable elements at differing radial positions and anasymmetric element.
 43. A position-indicating stent-graft comprising: aradially expandable tubular frame; a flexible liner supported by theframe; an attachment mechanism which holds the liner on the frame; andmarkers disposed on at least one of the frame, the liner, and theattachment mechanism,-the markers visible under imaging to indicate atleast one of axial and rotational position of the stent-graft.
 44. Aposition-indicating stent-graft as claimed in claim 43, wherein themarkers indicate position under imaging while in a compressed mode andwhile in an expanded mode.
 45. A position-indicating stent-graft asclaimed in claim 43, wherein the liner comprises a textile and themarkers comprise flexible radiopaque material bonded to the textile. 46.A position-indicating stent-graft as claimed in claim 45, wherein thetextile comprises polyester and the radiopaque material comprisestantalum and polyester bonded using a polyester solvent.
 47. Aposition-indicating stent-graft as claimed in claim 43, wherein themarkers comprise an overlap indicator to facilitate overlappingprosthetic modules within a predetermined range.
 48. Aposition-indicating stent-graft as claimed in claim 43, wherein themarkers comprise a rotational indicator.
 49. A position-indicatingstent-graft as claimed in claim 48, wherein the rotational indicatorcomprises alignable elements at differing radial positions about thestent-graft and an asymmetric element.
 50. A stent-graft placementmethod comprising: inserting a branching stent-graft into a patient bodyand positioning the branching stent-graft at a target location within abody lumen; expanding the branching stent-graft at the target location,the branching stent-graft comprising a tubular frame and a flexibleliner; supporting the liner with the frame at a first cross-section sothat the frame holds a common lumen open; supporting the liner with theframe at a second cross-section so that a first lobe of the frame holdsa first lumen of the liner open, and a second lobe of the frame holds asecond lumen of the liner open; and separating the first lumen from thesecond lumen with an isthmus of the frame disposed between the firstlobe and the second lobe.
 51. A method as claimed in claim 50, whereinthe supporting step at the second cross-section comprises supporting thefirst lumen with adjacent portions of first and second indentations andsupporting the second lumen with adjacent portions of the first andsecond indentations, the first and second indentations defining theisthmus of the frame.
 52. A method as claimed in claim 50, wherein theexpanding step comprises releasing the frame to expand resiliently atthe target location.
 53. A method as claimed in claim 52, wherein theexpanding step comprises plastically expanding at least a portion of thestent-graft at the target location.
 54. A method as claimed in claim 50,further comprising inserting an end of a tubular branch prosthesis intoone of the first and second-lumen and expanding the end of the branchprosthesis.
 55. A branching endoluminal stent-graft placement methodcomprising; inserting a branching stent-graft into a patient body andpositioning the branching stent-graft at a target location within a bodylumen; expanding the branching stent-graft at the target location, thebranching stent-graft comprising a tubular frame and an inelastic liner;and holding the liner in an open configuration with the frame so that aperimeter of a common lumen of the liner is smaller than a sum of aperimeter of a first branch lumen of the liner and a perimeter of asecond branch lumen of the liner.
 56. A method as claimed in claim 55,wherein the expanding step comprises releasing the frame to expandresiliently at the target location.
 57. A method as claimed in claim 55,wherein the expanding step comprises plastically expanding at least aportion of the stent-graft at the target location to match a branchingbody lumen.
 58. A method for treating a bent target region of a bodylumen comprising: inserting an endoluminal prosthesis into the bodylumen in a radially compressed configuration, the prosthesis having abend defining a preset angle when in an expanded configuration;positioning the prosthesis at the bent target region; rotationallyaligning the preset angle of the prosthesis with the bent target region;and expanding the aligned prosthesis at the bent target region.
 59. Amethod as claimed in claim 58, wherein the expanding step comprisesreleasing the frame to expand resiliently at the bent target region. 60.A method as claimed in claim 58, wherein the rotationally aligning stepcomprises imaging rotational markers on the prosthesis.
 61. A method asclaimed in claim 58, wherein the positioning step comprises placing anend of the prosthesis within an end of a previously positionedprosthesis, and wherein the expanding step comprises immovably engagingthe previously positioned prosthesis with the prosthesis end.
 62. Amethod as claimed in claim 58, wherein the positioning step comprisesplacing a main body portion of the prosthesis within the abdominalaorta, the bend directing a branch portion of the prosthesis along oneof the iliac arteries, and the preset angle being in the range between15° and 90°.
 63. A method for producing a branching stent-graftcomprising: producing a flexible tubular liner having a main body, afirst branch extending from the main body and a second branch extendingfrom the main body; selectively shrinking at least a portion of the mainbody relative to at least one of the first branch and the second branch;attaching a radially compressible frame to the tubular liner.
 64. Amethod as claimed in claim 63, wherein a perimeter of the main bodyportion is shrunk by up to 20% relative to a perimeter of the at leastone of the first branch and the second branch.
 65. A method forproducing a branching endoluminal prosthesis, the method comprising:fabricating a resilient tubular frame; expanding-the frame to anexpanded configuration; heat-treating the expanded frame whilerestraining the expanded frame so that a cross-section of the framedefines two lobes separated by at least one indentation; attaching aflexible liner to a first lobe and an adjacent portion of the at leastone indentation so that a first lumen of the liner is held open by theframe.
 66. A modular endoluminal prosthesis placement method comprising:inserting a Y-connector prosthetic module within a body lumen system;positioning a main body of the Y-connector prosthetic module at a targetlocation of a body lumen, the target location adjacent to first andsecond branch lumens of the body lumen system; radially expanding thefirst prosthetic module at the target location; selecting a preferredfirst branch prosthetic module from a plurality of alternative branchprosthetic modules having differing prosthetic characteristics; andpositioning an end of the preferred first branch prosthetic modulewithin the first branch of the body lumen system and radially expandingthe preferred first branch prosthetic module, the expanded preferredfirst branch prosthetic module engaging the Y-connector prostheticmodule.
 67. A method for assembling endoluminal prosthetic moduleswithin a body lumen, the method comprising: deploying a first tubularprosthetic module within the body lumen; inserting a second tubularprosthetic module into the body lumen in a radially compressedconfiguration; aligning an image of markings disposed on at least one ofthe first prosthetic module and the second prosthetic module with animage of the other of the first prosthetic module and the secondprosthetic module; and expanding an end of the aligned second prostheticmodule to engage an end of the first prosthetic module.
 68. A method asclaimed in claim 67, wherein the aligning step comprises overlapping theends of the first and second prosthetic modules within a predeterminedrange as indicated by an overlap marker band.
 69. A method as claimed inclaim 67, wherein the aligning step comprises orienting an asymmetricmarker element in a generally direction and bringing together the imageof alignable marker elements, the marker elements disposed at differentradial positions about the second prosthetic module.
 70. A method forpositioning endoluminal prosthetic modules within a body lumen, themethod comprising: inserting a tubular prosthesis into the body lumen ina radially compressed configuration; imaging markings disposed on theinserted prosthetic module; rotationally orienting an asymmetric markerelement and bringing together the image of marker disposed atdifferent-radial locations about the prosthesis to align the prosthesis;and expanding the aligned prosthesis within the body lumen.